Journal of Threatened Taxa |
www.threatenedtaxa.org | 26 April 2018 | 10(5): 11665–11671
Water
striders, the genus Cylindrostethus Mayr (Insecta: Heteroptera: Gerridae) from India
with a new record
E. Eyarin
Jehamalar1, Kailash Chandra2 & G. Srinivasan3
1,2 Zoological Survey of India, Prani Vigyan Bhawan,
Block M, New Alipore, Kolkata, West Bengal 700053, India
3 Zoological Survey of India, Marine Biology Regional
Centre, Santhome High Road, Chennai, Tamil Nadu
600028, India
1 jehamalar@gmail.com (corresponding author), 2 kailash611@rediffmail.com,3 gurusrinivasanzsi@gmail.com
Abstract: The genus Cylindrostethus
Mayr, 1865 from India is studied. Prior to this study C. productus (Spinola, 1837) and
C. scrutator (Kirkaldy,
1899) of Cylindrostethus were known from
India. The record of C. scrutator (Kirkaldy, 1899)
from India is doubtful. Study of gerrid specimens from Andaman Islands revealed one more
additional species, C. costalis costalis Schmidt, 1915 new to
Indian fauna. So, presently two
species of this genus are known from India namely C. costalis
costalis and C. productus,
both belonging to the C. costalis species
group (Polhemus 1994). A detailed study has been made of the
male and female genitalia of Cylindrostethus
known from India.
Keywords: Cylindrostethinae, first
record, India, water striders, taxonomy.
doi: http://doi.org/10.11609/jott.3750.10.5.11665-11671
| ZooBank: urn:lsid:zoobank.org:pub:E70077F0-ED51-4880-B8BC-8C114E3859E0
Editor:
Dan A. Polhemus,
Smithsonian Institution, Washington, USA. Date of publication: 26 April 2018
(online & print)
Manuscript
details: Ms # 3750 |
Received 28 May 2017 | Final received 04 April 2018 | Finally accepted 11 April
2018
Citation: Jehamalar, E.E., K. Chandra & G. Srinivasan
(2018).
Water striders, the genus Cylindrostethus Mayr (Insecta: Heteroptera: Gerridae) from India
with a new record. Journal of Threatened Taxa 10(5): 11665–11671; http://doi.org/10.11609/jott.3750.10.5.11665-11671
Copyright: Jehamalar et al. 2018. Creative Commons
Attribution 4.0 International License. JoTT
allows unrestricted use of this article in any medium, reproduction and
distribution by providing adequate credit to the authors and the source of
publication.
Funding: None.
Competing interests: The authors declare no competing interests.
Acknowledgements: The authors
thank Zoological Survey of India for the facilities. We are thankful to Dr.
Herbert Zettel, International Research Institute of
Entomology, Natural History Museum, Vienna, Austria, for sharing his knowledge
on the group. The authors also thank Dr. Dan A. Polhemus,
Department of Natural Sciences, Bishop Museum, Honolulu, USA, and Miss. Carla
Fernanda Burguez Floriano,
So Paulo State University (UNESP), Assis, So Paulo,
Brazil, for providing literature. We are thankful to Mr. M.D. Webb, Curator of Hemiptera, Natural History Museum, London, for sending
photographs of the types and other specimens with locality label as India of C.
scrutator. We thank Dr. C. Raghunathan,
Officer-in-Charge, Entomology Division, ZSI-HQ, Kolkata, for making
arrangements of field trips to Andaman Islands. We also thank Dr. M. E. Hassan,
Officer-in-Charge, Hemiptera Section, ZSI, Kolkata,
for cooperation in the study of backlog materials. Thanks are due to Dr. Tran Anh Duc, Department of
Invertebrate Zoology, Hanoi University of Science, Vietnam, for valuable inputs
on the manuscript.
The
subfamily Cylindrostethinae comprises three genera: Cylindrostethus Mayr,
1865, Platygerris Buchanan-White, 1883,
and Potamobates Champion, 1898. The latter two are strictly confined to
the Neotropical region. Cylindrostethus
are very long and slender water striders with body lengths ranging from
8.74–27 mm, inhabiting partial to well-shaded, slow flowing forest
streams and sometimes estuaries near river mouths. Cylindrostethus
can easily be distinguished from Platygerris
and Potomobates by the straight posterior
margin of pronotum, less prolonged eighth abdominal
segment of the male, non-rotated abdominal segment VIII and IX of the male,
simple postero-median margin of abdominal sternum VII
in the female, and mostly visible abdominal sternum VIII of the female. The genus Cylindrostethus
presently contains 18 species (including two nominotypical
subspecies) and three subspecies, distributed in the Neotropical,
Ethiopian and Oriental regions (see Hungerford & Matsuda 1962; Linnavuori 1981; Polhemus 1994; Floriano & Cavichioli 2013; Zettel et al. 2017).
The Old World species of Cylindrostethus
were revised by Hungerford & Matsuda (1962) and Polhemus
(1994). The present paper provides
the first record of C. costalis costalis from India (the Andaman Islands) and
accompanied by photographs showing detailed morphological characteristics of
the two species known from India to facilitate easy identification.
Material and Methods
The
studied materials were collected from very cool and well shaded, slow flowing
forest streams of India by using a D-frame aquatic insect net, and preserved in
75% ethanol. The photographs and
measurements were taken through a Leica stereo zoom microscope (Leica M205A),
using the software Leica application suite (LAS V3.8). All measurements are given in mm. All the studied specimens are deposited
in National Zoological Collection, Hemiptera Section,
Zoological Survey of India, Kolkata, India, except that the specimens collected
from Madhya Pradesh are deposited in Central Zone Regional Centre, Zoological
Survey of India, Jabalpur, Madhya Pradesh, India.
Taxonomy
Cylindrostethus Fieber,
1861
Notes: For a detailed
description of the genus, see Hungerford & Matsuda (1962) and D. Polhemus (1994).
Cylindrostethus costalis
costalis Schmidt, 1915
(Images 1A–P)
1915.
Cylindrostethus costalis
Schmidt, Stett. Ent. Zeit., 76: 364.
2017.
Cylindrostethus costalis
costalis Schmidt: Zettel
et al. Aquatic insects, 38(1–2): 30.
Material examined: Reg. No. 4048/H15, 6.iii.2012, 2
apt. males, 3 apt. females, India:
Andaman & Nicobar Islands, Andaman District, South Andaman Island, Mongulton, 11.791666670N & 92.732500000E,
14.02m, coll. E. Eyarin Jehamalar;
Reg. No. 4047/H15, 16.xii.2013, 1 apt. male, 2 mac. males, 3 mac. females, North
Andaman Island, Saddle Peak National Park, a stream near Forest Camp,
13.477222220N & 92.176111110E, 14.6m, coll. G. Srinivasan; Reg. No. 4046/H15, 10.i.2014, 2 mac. females, Saddle Peak National Park, Sindhur
Nala, 13.326944440N & 93.155555560E,
15m, coll. G. Srinivasan.
Diagnosis:
Cylindrostethus costalis costalis can readily be identified by the presence of a yellowish costal margin
on the forewing (Image 1A,B,F), the absence of spinules on the mesosternum and
the presence of spinules on the posterior region of
the metasternum (Image 1E), and the presence of a
broad longitudinal yellow stripe on the thorax, except on the metanotum; absence of spinules on
the pygophore of the male (Image 1K, L); and the
shape of the lateral process on the male proctiger
(Image 1N).
Descriptive
notes: Apterous male: (Image 1C, E, G, H, K–O).
Body length 17.01 (range 16.47–17.28); body width (across mesacetabula) 2.83 (range 2.63–2.83).
Colour:
Dorsum
black and shiny, ventral yellow; head between eyes yellow to orange; yellow
median line on thorax continues up to abdominal tergum
IV, mostly absent on metanotum and indistinct on
abdominal tergum II (Image 1C); antero-ventral
side of fore femur one third from base with a broad black stripe and reaching
up to one fourth distance from base and not confluent with ventral black apical
ring of fore femur, black stripe on flexor region of fore femur confluent with
black apical ring; tibia and tarsus of all legs black except hind tibia orange;
mid and hind tibia outer margin with a longitudinal black stripe; dorsolateral
region of meso- and metacetabula
with black longitudinal stripe; sublateral region of
abdominal sterna with a black longitudinal stripe; abdominal terga I–IV with median longitudinal yellow stripe
interrupted between joints (indistinct in abdominal tergum
II); dorsal connexival margin yellow, connexival spine basolateral
region and subapex brown (Image 1G, H), lateral
region of tergum VIII yellow.
Structural
characters: Body
venter clothed with minute silvery-white hairs; head length 1.54, head width
1.89, eyes convergent anteriorly near vertex, dorsal inner margin concave and
slightly depressed, minimum interocular width 0.47,
eye length 0.96, eye width 0.57; last antennal segment slightly curved (Image
1C), antennal segment lengths I–IV 2.41, 1.03, 0.77, 1.06; posterior
region of metasternum to sternum VII clothed with
black spinules, except sublateral
regions; dorsal thorax length 5.97, pronotal length
1.21, pronotal width 1.91, mesonotal
length 3.42, metanotal length 1.45, prosternal length 0.84, mesosternal
length 4.13, metasternal length 2.09, metasternal scent channel prominent; flexor region of fore
femur with a few dispersed setae, flexor region of fore femur subapically with a short blunt tooth; flexor region of fore
tibia fringed with minute setae, fore tibia slightly inwardly curved apically,
inner apical process of fore tibia blunt; all legs with prominent claws; mid
and hind legs clothed with minute spines; inner margin of hind tibia and tarsus
fringed with short curved setae. Lengths of leg segments: Fore leg:
femur 4.30 (4.16–4.26), tibia 3.87 (3.84–3.87), tarsomeres
I–II 0.20 (0.20–0.25), 0.61 (0.52–0.61); mid leg: femur 14.47
(13.86–14.47), tibia 10.23 (9.23–10.23), tarsomeres
I–II 4.84 (4.42–4.84), 0.94 (0.83–0.94); hind leg: femur
15.74 (15.23–15.74), tibia 9.92 (9.24–9.92), tarsomeres
I–II 0.58 (0.52–0.58), 0.35 (0.30–0.35). Width
of fore femur 0.72 (0.68–0.72). Venter of abdominal sterna medially with
a faint longitudinal ridge, sublateral region of
second abdominal sternum with a longitudinal carinae
adjacent to hind coxa and trochanter (Image 1E);
length of abdominal terga I–VIII 0.58, 1.08,
1.08, 1.10, 1.08, 1.10, 1.27, 0.75, dorsal proctiger
length 0.76; length of abdominal sterna II–VIII 1.18, 1.05, 1.05, 1.12,
1.07, 0.78, 0.91, pygophore length 1.05, ventral proctiger length 0.09; connexival
process reached up to level of abdominal tip or little surpassing abdominal
tip, length 1.48. Genitalia: pygophore suddenly acuminated near apex, spinules absent, ventrolateral
region along midway fringed with setae (Image 1H, K, L); proctiger
highly sclerotised, apical margin with eleven short
stout spines, sub-basal region with lateral processes, left process broader
than right process, base of lateral processes with a few long setae, proctiger produced and tongue-like below lateral processes
(Image 1G, N); endosomal sheath highly sclerotised, dorsal and ventral endosomal
sclerites united, ventral sclerite
less sclerotised coiled and enclosed round central sclerite (cs–term newly
proposed here), dorsal sclerite bent forwards but not
extending one third distance from base of endosoma,
lateral sclerites boat-shaped with apical region
appearing as folded hands in prayer shape in lateral aspect, single apical sclerite long and linear, placed ventrally, upper region of
endosoma infront of dorsal sclerite with ring-like impression up to subapex (Image 1O); parameres
slightly visible from outside, symmetrical and narrowed medially (Image 1M).
Macropterous male (Image 1A, F):
Similar to apterous male with following exceptions:
body length 17.34–17.74, width 2.88–2.95, pronotal
lobe length 5.06–5.32, width 2.20–2.24, hemelytral length
9.94–10.30, width 1.20–1.35. Median longitudinal yellow line
confined to anterior pronotal lobe; lateral region of
posterior pronotal lobe anteriorly with thin and
posteriorly with thick yellow border; humeral angle slightly produced; wings
dark brown to black, not exceeding posterior margin of tergum
VII, two third from the base of hemelytral costal margin with yellow line
(Image 1A).
Apterous female (Image 1D, I, J):
Similar to apterous male, but a little larger (mostly
measurements are given here). Body length 18.29 (range 17.93–18.86), body
width (across mesacetabula) 2.91 (range
2.85–3.06), head length 1.65, width 1.93, minimum interocular
width 0.43, eye length 1.04, eye width 0.69, antennal segment lengths
I–IV 2.55, 1.17, 0.73, 1.11; dorsal thorax length 6.69, pronotal length 1.23, pronotal
width 1.94, mesonotal length 3.88, mesonotum without any tubercle on postero
sublateral region (Image 1D), metanotal
length 1.59, prosternal length 0.87, mesosternal length 4.19, metasternal
length 2.01. Lengths of leg segments: Fore leg: femur 4.16
(4.16–4.59), tibia 3.93 (3.93–4.20), tarsomeres
I–II 0.24 (0.17–0.24), 0.56 (0.56–0.63); mid leg: femur 15.24
(14.59–15.67), tibia 10.58 (10.02–10.98), tarsomeres
I–II 4.96 (4.78–4.99), 0.93 (0.89–0.94); hind leg: femur
16.05 (15.79–16.95), tibia 10.62 (10.09–10.77), tarsomeres
I–II 0.63 (0.57–0.65), 0.36 (0.35–0.36). Width
of fore femur 0.72 (0.70–0.72). Length of abdominal terga
I–VIII 0.59, 1.22, 1.29, 1.29, 1.28, 1.25, 1.37, 0.79, dorsal proctiger length 0.64; length of abdominal sterna
II–VII 1.49, 1.23, 1.25, 1.24, 1.28, 1.47, length of gonocoxa
0.79, ventral proctiger length 0.46; connexival process length 1.92, distinctly surpassing tip
of abdomen.
Macropterous female (Image 1B, P):
Similar to macropterous male with following
exceptions: connexival process mostly distinctly
surpassing abdominal tip. Body length 18.29–18.83,
width 3.04–3.17, pronotal lobe length
5.20–5.50, width 2.21–2.31, hemelytral length 10.02–10.51,
width 1.24–1.41. Genitalia: gonapophyses
highly sclerotised, first gonapophysis
(go1) outer margin fringed with long setae, second gonapophysis
(go2) without any characteristic long setae; processes of both first and second
gonapophysis (gop1, gop2) clothed with sparse setae,
length of gop1 0.36, width 0.11, length of gop2 0.51, width 0.09, tip of first gonapophysial process (gop1) with a long inwardly curved
peg-like seta (ps), length of ps
0.19, width 0.02, gop1 1.9 times as long as ps; base
of second gonapophysial processes connected each
other by gonapophysial copulator
(goc- term newly proposed here), a wavy line (wl) originating from outer lateral region of gop2 united
with goc at level of origin, non-sclerotised
area near wavy line large and prominent, proctiger
length 0.86 (Image 1P).
Distribution:
India
(Andaman Islands, a first record for India); Cambodia, Laos, Myanmar, Thailand,
Vietnam (Hungerford & Matsuda 1962; D. Polhemus
1994; Zettel & Chen 1996; Zettel
et al. 2017).
Cylindrostethus productus
(Spinola, 1837)
(Image 2A–I)
1837.
Gerris productus
Spinola, Essai sur les Insectes Hmiptres Rhyngotes Htroptres, 64.
1962.
Cylindrostethus productus
(Spinola), Hungerford & Matsuda, Univ.
Kansas Sci. Bull., 63: 86-89.
Material examined: Reg. No. 3198/H15, 2.x.2013, 2
mac. males, 1 apt. male, 2 mac. females, 20 nymphs, India: Chhattisgarh, Durg
District, Balod Range, Tandola
Dam, coll. A. Raha and Party; Reg. No. 2726/H15,
27.v.2012, 4 apt. males, 1 mac. female,
2 apt. females, Jashpur
District, Badalkhol WS, Khara
Nala, coll. A. Raha and
Party; Reg. No. 3425/H15, 22.iii.2014, 5 mac. males, 4
mac. females, 1 apt. female, Awra Nala, coll. E.E. Jehamalar; Reg. No. 2550/H15, 18.xi.2011, 4 males, 5
females, Kabirdham District, Bhoremdev
WS, Sunwahi Forest, coll. S.K. Gupta and Party; Reg.
No. 3053/H15, 26.viii.2011, 1 apt. male, Chilpighati, coll. S.K. Gupta and Party; Reg. No. 2552/H15,
22.xi.2011, 7 mac. males, 9 mac. females,
Jamunpani forest, coll. Angshuman;
Reg. No. 3420/H15, 1.iv.2014, 2 mac. males, 7 mac. females, Chilpi, Bagbil, coll. E.E. Jehamalar;
Reg. No. 3431/H15, 27.iii.2014, 1 mac. female, Korba District, Bijakhara Nala, coll. E.E. Jehamalar; Reg.
No. 3129/H15, 15.vii.2011, 1 mac. male, Raipur
District, Barnawapara WS, Lalbandha
Palaca, coll. S.K. Gupta and Party; Reg. No.
3088/H15, 14.v.2013, 1 apt. male, 1 apt. female, 2 nymphs, Surguja
District, Ramkola, Tamor-Pingla
WS, Pingla Nala, coll. P.
Dawn., Reg. No. 3196/H15, 28.viii.2013, 2 apt. males,
2 apt. females, 2 Nymphs, Kerala, Kozhikode District, Nanminda, coll. P. Girish Kumar;
Reg. No. 4049/H15, 26.i.1961, 3 apt. males, 6 mac. males, 7 mac. females, Madhya
Pradesh, Balaghat District, Muki,
coll. B.S. Lamba; Reg. No. A/13417, 22.iii.1990, 26
males, 24 females, Betul District, Katawadi, coll. H.S. Sharma and Party; Reg. No. A/13423,
5.iv.1979, 9 males, 8 females, Hoshangabad District, Apsara Bihar, Pachmari, coll.
P.D. Rane; Reg. No. A/13421, 12.vi.1999, 3 males, 8
females, Bori Sanctuary, Churna,
Bhaisa Nala, coll. K.
Chandra; Reg. No. A/13420, 9.iii.2000, 2 males, 1 female, Pachmari, coll. R.K. Singh; Reg. No. A/13409, 4.iv.2001, 1 female, Panarpani,
coll. Y.N. Gupta and Party; Reg. No. A/13412,
14.vii.1964, 3 females, Jabalpur District, Pariat
Forest, coll. H.P. Agrawal; Reg. No. A/13411,
29.vi.1965, 4 females, 2km east of Bargi FRH, coll.
H. Khajuria; Reg. No. A/13414, 22.i.1969, 10 males,
21 females, Dindori Road, Fagna
Nala, coll. V.S. Durve;
Reg. No. A/13415, 26.iv.1969, 40 males, 26 females, Rani Durgavathi Samathi Road, coll.
V.S. Durve; Reg. No. A/13422,
5.ix.1969, 2 males, 4 Nymphs, Bargi Village, coll.
H.P. Agrawal; Reg. No. A/13413,
16.xii.1971, 22 males, 34 females, Bhedaghat, coll.
R.K. Singh and Party; Reg. No. A/13418, 5.iii.1983, 10 males, 8 females,
Mandla District, Garam Pani Kund, coll. U.A. Gajbe; Reg. No. A/13410, 1.iii.1994, 1 male, 1 female, Seoni District, Patalkot, coll.
H.S. Sharma; Reg. No. A/13416, 4.ii.1980, 7 males, 13 females, Shahdol District, Amarkantak,
coll. P.D. Rane and Party; Reg. No. A/13407, 5.ii.1980, 28 males, 22 females, Kapildhara,
coll. P.D. Rane and Party; Reg. No. 4050/H15,
3.i.1976, 8 mac. males, 3 mac. females, Odisha, Dhenkanal District, Purnakot,
coll. D.P. Sanyal and A.K. Sarkar;
Reg. No. 4051/H15, 19.iii.1973, 6 mac. males, 10 mac. females, Mayurbhanj District, Meghasani Forest, coll. S.K. Gupta; Reg. No. 4053/H15,
6.i.1974, 3 mac. males, 2 mac. females,
Puri District, Berbera,
coll. R.L. Chowdhury; Reg. No. 4054/H15, 13.ix.1972,
2 apt. females, 1 Nymph, Sundargarh
District, Kurodhi River, Barsuan
Village, coll. S. Khera and Party; Reg. No. 4275/H15,
25.ix.2009, 19 apt. males, 17 apt. females,
4 mac. males, 3 mac. females,
7 Nymphs, Tamil Nadu, Kanyakumari District, Manakudy Estuary (near river mouth), coll. J.A. Angelin; Reg. No. 2534/H15, 5.x.2011, 3 apt. males, 5 apt. females, 1 mac. female, Cherukole Village, coll.
E.E. Jehamalar; Reg. No. 2825/H15, Chithiramcode, 23.x.2012, 1 mac. female,
coll. E.E. Jehamalar and E.H.R. Deasingh;
Reg. No. 3052/H15, Churulode, 26.x.2012, 1 apt. male, 4 apt. females, coll. E.E. Jehamalar and E.H.R. Deasingh;
Reg. No. 4052/H15, 15.v.1968, 1 apt. male, 3 apt. females, Uttarakhand, Dehradun
District, Kansro Forest, coll. Asket
Singh.
Diagnosis:
Cylindrostethus productus can easily be
identified by the absence of a yellow costal margin on the forewing (Image 2F),
the presence of the spinules on the mesosternum, metasternum and the
abdominal sterna II-VII; the presence of a pair of tubercles on the mesonotum of the apterous female
(Image 2A); the presence of the spinules on the pygophore of the male (Image 2B, C); the unique shape of
the lateral process on the male proctiger (Image 2D);
the basally broad male paramere (Image 2E); the
presence of a long stalk-like conjunctivum (ct) coupled with the absence of coiled ventral sclerite, (Image 2G); the shape of the wavy line on the
process of second gonapophysis of the female
genitalia and the proportion of the process of the second gonapophysis
and its peg-like setae (Image 2H).
Descriptive
notes:
(The detailed description of C. productus has
been given by Hungerford & Matsuda, 1962, so, only body length, width and
characters of genitalia of male and female are given here). Body
length, mac. male 22.06–22.67, mac. female 22.42–23.64, apt. male
21.93–22.53, apt. female 23.36–24.47; body
width mac. male 3.12–3.24, mac. female 3.22–3.42, apt. male
2.95–3.14, apt. female 3.10–3.44. Male
Genitalia: pygophore gradually acuminated near apex,
nearly forty spinules present on dorsal apical region
(Image 2B, C); proctiger highly sclerotised,
produced tongue-like below lateral processes, apical margin with nearly
twenty-three short stout spines, sub-basal region with lateral processes, left
process slightly broader than right process, outer margin of left process
indented, base of lateral processes with a few setae (Image 2D); endosomal sheath highly sclerotised,
lateral sclerites well developed, boat-shaped, not
appearing as folded hands in prayer in lateral aspect, apical region broad,
outer margin concave and inner margin convex in dorsal aspect, other sclerites not prominent or absent, conjunctivum
of endosoma long, robust, and curved (Image 2G, I); parameres symmetrical with broad base, upper sub-basal
region with less sclerotised area, apical region with
few spinose setae (Image 2E). Female Genitalia: gonapophyses highly sclerotised,
first gonapophysis (go1) outer margin fringed with
long setae, second gonapophysis (go2) without any
characteristic long setae; processes of both first and second gonapophyses (gop1, gop2) clothed with sparse setae, length
of gop1 0.46, width 0.10, length of gop2 0.54, width 0.09, tip of first gonapophysial process (gop1) with a long curved peg-like
setae (ps), length of ps
0.18, width 0.01, gop1 2.5 times as long as ps; base
of second gonapophysial processes connected each
other by gonapophysial copulator
(goc), a wavy line (wl)
originating from outer lateral region of gop2 united with lateral margin of
go2, non-sclerotised area near wavy line small, proctiger length 1.04 (Image 2H).
Distribution:
India
(Chhattisgarh, Karnataka, Kerala, Madhya Pradesh, Maharashtra, Odisha, Punjab, Tamil Nadu, Uttarakhand,
Uttar Pradesh and West Bengal), Nepal, and Sri Lanka (Polhemus
1994; Thirumalai 2002).
Discussion
Prior
to the present study, only two species of Cylindrostethinae,
Cylindrostethus productus
and C. scrutator, were known from India (Thirumalai 2002).
Hungerford & Matsuda (1962) indicated that they had examined two apterous males and one apterous
female of C. scrutator from India, but did not
provide any specific locality data. These specimens were deposited in the
British Museum. Polhemus
(1994) suspected that the record of C. scrutator by
Hungerford & Matsuda (1962), was probably from
Assam. C. scrutator,
however, has not been encountered in several surveys conducted by
scientists from Zoological Survey of India over the past hundred years and
therefore the record of C. scrutator from
India is doubtful. In the old colonial period, India was a term used for a
much larger region, including Myanmar. Cylindrostethus
scrutator is relatively common on the Greater Sunda Islands (Sumatra, Java, and Borneo) and also occurs
in southern Myanmar, central Thailand and southern Vietnam within continental
Southeast Asia. It appears very
unlikely that the species occurs in India (Dr.
Herbert Zettel pers. info. 2014). The authors have
seen photographs of the specimens of C. scrutator,
sent by Mr. M.D. Webb, Curator of Hemiptera, Natural History Museum, London, which were examined
by Hungerford and Matsuda. It seems
one is an apterous male from Tavoy
(Myanmar) and another from Tenasserim (Myanmar) and
one specimen without locality. So
the record of C. scrutator from India remains
doubtful.
The
present record of C. costalis costalis
from the Andaman Islands adds one more species to the fauna of India. This record is quite interesting and is
of zoogeographical importance, because the Andaman Islands are considered as
the exposed part of the long Arakan Yoma Mountain range of Myanmar, in the Bay of Bengal. Cylindrostethus
costalis costalis is
widely distributed in Cambodia, Laos, Myanmar, Thailand and Vietnam, but not
southern China or Peninsular Malaysia (D. Polhemus
1994; Zettel et al. 2017). Cylindrostethus
productus is distributed only in Sri Lanka, Nepal
and mainland India (D. Polhemus 1994; Thirumalai 2002).
Both C. costalis costalis
and C. productus belong to the same
species group, but possess major differences in the male genitalia,
particularly in the endosomal sclerites. The posterior region
of the pygophore in the males of C. productus possess spinules,
but such spinules are absent on the posterior region
of the pygophore of C. costalis
costalis.
In C. productus, only the lateral sclerites are prominent and the other sclerites
such as dorsal, ventral and apical sclerites are
absent, however all these sclerites are present in C.
costalis costalis. The
absence of endosomal sclerites,
except lateral sclerites, in C. productus may have evolutionary significance and needs
phylogenetic study. The female
genitalia of both the species are similar in appearance, but specific
differences are seen between the species. The proportion of the peg-like seta
and the second gonapophysis and the wavy line on the
second gonapophysis (Image 1P, 2H) can be considered
as the significant characters for identification of the females, if males are
absent in collections. The
evaporative channel or groove on the metasternum
forms a short segment-like portion on the posterior region of the metasternum, which often creates confusion as to the
position of abdominal sternum I, but the detailed study after removing the
muscles lying in the metathorax shows that the part
above abdominal sternum-II is a part of metasternum
(Image 1E).
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